The existing secret file access authorization system does not have the secret file access authorization function with environment limitation and time limitation; take the file safe technique for example, an encrypted memory area is established in a computer to store secret files, and a user must have the authorization secret key to access the secret files in the encrypted memory area. However, the secret files can be accessed by anyone without the secret key when they are duplicated to other computers. As shown in FIG. 1, the files protected by PGPDISK can be copied to unencrypted Disk B which can be taken anywhere, thus losing authority control. It is very obvious that there is no environment limitation to PGPDISK encryption/decryption, i.e., even though the files which are taken are encrypted, they can also be accessed elsewhere so long as the PGPDISK software is installed.
Another existing technique is the secret file encryption technique. The encrypted secret files could be accessed only with the authorization secret key. However, if the secret files are transferred to an illegal environment (e.g., stolen to home or abroad), they can still be accessed if the authorization secret key is available. In other words, a kind of “position authorization” mechanism is needed for the authorization of secret files, i.e., only when the authorization object of the secret files is in a certain position or under a certain condition can he/she have the authority to access the secret files, and once his/her position changes or the authorization condition disappears, he/she should not have the authority to access to the secret files anymore. This can not be done according to the existing access authorization technique.